Disable encoder scaling on iPhone4S.

webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm

Index: webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm b/webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm
index 51003cad4113dc5a01c3aa4dff07a872303b6381..7c80889418086e447cb7325e2b6cedd06ed6cd04 100644
--- a/webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm
+++ b/webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm
@@ -575,6 +575,7 @@ AVFoundationVideoCapturer::AVFoundationVideoCapturer()
 #if TARGET_OS_IPHONE
   if ([UIDevice deviceType] == RTCDeviceTypeIPhone4S) {
     supported_formats.push_back(cricket::VideoFormat(kIPhone4SFormat));
+    set_enable_video_adapter(false);

[mflodman, 2016/08/03 10:54:49]

Agree this is godo to have here, but in practice it shouldn't be needed with 
https://codereview.webrtc.org/2206773002/
in place, right? Or is this in case the camera would open with an even lower
resolution?

[tkchin_webrtc, 2016/08/03 18:03:34]

Technically not needed, but will skip some checks / lock grabbing at the very
least. Camera will not open in lower resolution.

   } else {
     supported_formats.push_back(cricket::VideoFormat(kDefaultFormat));
   }